"think that" or "think if" or think that if"

[iemortal]

Dear all,
Recently when teaching clause, I've encountered a problem:

1. Do you think that it will rain tomorrow?
2. Do you think if it will rain tomorrow?

Which one is correct? Or What is the difference?
According to our textbook, No. 2 is correct. But No. 1 seems all right to me because I would say that to my friends.

Thanks for your attention.

Cheers,
Edward

[Susan]

Number 2 is incorrect
Number 1 is correct
You can also say: do you think it will rain tomorrow.

[cerealkillah]

Number 2 may be correct, but the meaning is different. "if" in this case means "whether", so in the second sentence we ask not about opinion (sentence number one), but about the "activity of thinking" itself. It is the rare case, when "think" can come with -ing ending.
I think the film is awesome. vs I'm thinking about going to the cinema.

So, in theory both sentences are grammaticaly correct, but the second one is highly unusual.

[cerealkillah]

I think this will be best one - Do you think that it will going to rain tomorrow?

It isn't the best one. In fact, it is grammatically incorrect. It is either It will rain or it is going to rain (with the first one being more common in sentences with "think"). There is no such structure as "will going to".

[LeesaJohnson]

The second sentence is correct. You can also write a sentence "Do you think it will rain tomorrow?"